Question: K/T r vs. K regimes

Do you think the physical fragility of K/T birds was a liability vis a vis
other classes of land vertebrates (esp. mammals) in the post-K/T r regime?
Wouldn't the metabolism and power of flight be a big advantage in an r
regime after shift in primary selection from a K basis? I'm sure there were
still dinos the year after Chicxulub. But their 150MY+ trait adaptations
were far better suited to K than r, and the tops of the food chain are
longest-lived as well as biggest, and can't adapt as quickly in the face of
rapid changes in the ecological carrying capacity or in
same-capacity-different-habitat changes. In 500 years they get 10-20
generations; the (small) birds and mammals get 100-500+ (how do those shrews
do it?). Not to mention that in famine, the top of the food chain can be
lopped off altogether - eg Australia's limited fauna (Jared Diamond wrote an
interesting article on the topic a year or so ago in Discover, I think).
It would be interesting to know the # of sub-10kg bird vs. mammal vs. dino
species present in latest Cretaceous strata. They were all fragile; were
they comparably fragile, or is the record skewed by differences between
classes?